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Xref: sserve comp.os.os2.programmer.misc:9631 comp.os.linux.development:8778 comp.os.minix:23671 comp.os.mach:3770 comp.periphs:5442 comp.unix.bsd:13892 comp.unix.pc-clone.32bit:6180 comp.os.386bsd.development:2066 comp.sys.ibm.pc.hardware.misc:5073 Path: sserve!newshost.anu.edu.au!munnari.oz.au!bunyip.cc.uq.oz.au!harbinger.cc.monash.edu.au!msuinfo!agate!howland.reston.ans.net!cs.utexas.edu!swrinde!hookup!news.kei.com!eff!neoucom.edu!kira.cc.uakron.edu!malgudi.oar.net!oclc.org!oclc.org!not-for-mail From: aph@oclc.org (Andrew Houghton) Newsgroups: comp.os.os2.programmer.misc,comp.os.linux.development,comp.os.minix,comp.os.mach,comp.periphs,comp.unix.bsd,comp.unix.pc-clone.32bit,comp.os.386bsd.development,comp.sys.ibm.pc.hardware.misc Subject: Re: [Announcement] 386BSD Release 1.0 Followup-To: comp.os.os2.programmer.misc,comp.os.linux.development,comp.os.minix,comp.os.mach,comp.periphs,comp.unix.bsd,comp.unix.pc-clone.32bit,comp.os.386bsd.development,comp.sys.ibm.pc.hardware.misc Date: 6 May 1994 17:54:10 -0400 Organization: OCLC Online Computer Library Center, Inc. Lines: 21 Distribution: world Message-ID: <2qeea2$j37@oclc.org> References: <2q63q2$927@dearg.cuillin.org.uk> <wright.86.000DC700@lims01.lerc.nasa.gov> <2q8qqr$q96@spool.cs.wisc.edu> <hastyCpCLny.5q8@netcom.com> <newcombe.142.00141E4A@aa.csc.peachnet.edu> <2qdvvp$r@bmerha64.bnr.ca> NNTP-Posting-Host: fssun10-30.dev.oclc.org X-Newsreader: TIN [version 1.2 PL2] Jean Cyr (jcyr@bnr.ca) wrote: : Can't be done. The initial boot stage (reading the boot sector and jumping to it) : is handled by your machine's BIOS rom. Currently all BIOS that I've seen look : for boot sectors on floppy and hard disk. They never look for CD. How could they ? : There's no BIOS support for CD. Yes it can. Everyone's BIOS, from an IBM XT on up, goes thru the ROM address space looking for a specific signature at every 4K or 8K (I forget which) address boundry between C0000-D0000. When the BIOS finds an appropriate signature it then executes the code following the signature. Disk and SCSI controller manufactures map their ROM on their controller board into the ROM address space. Once their code is executed they can do anything to the CPU including revectoring *key* BIOS interrupt vectors so when the BIOS later goes to read the master boot partition the call goes to the SCSI controller, which allows a CDROM drive to boot without an OS already running. -- Andrew P. Houghton, MC 265 Internet: aph@oclc.org OCLC Online Computer Library Center, Inc. 6565 Franz Road Dublin, Ohio USA 43017-0702 NeXT Mail accepted.